This invention relates to a novel method for recovering nickel and ferronickel from waste materials and spent catalysts containing nickel and more particularly, to an inexpensive and novel method for improving the nickel content and/or production of ferronickel.
As is well known to those skilled in the art, nickel-containing catalysts are used in many reactions such as hydrogenation reactions, alkylation reactions, hydroalkylation reactions, cracking processes, etc. Initially, these catalysts perform at a high level, but as the reaction proceeds, the catalyst becomes less active. Eventually, the activity of the catalyst decreases to a point where it is not sufficiently effective to be used in a commercial process.
A wide variety of nickel catalysts and modifications thereof have been described in the art in which they are utilized. Nickel catalysts are used extensively in hydrogenation reactions such as in the hydrogenation of unsaturated organic compounds. Usually, catalysts which are used in hydroalkylation reactions will contain in addition to nickel, other metals such as tungsten. Nickel catalysts used in cracking operations often contain molybdenum and other elements. Other nickel catalysts may contain iron and/or aluminum in small amounts.
Considerable research has been conducted on methods for regenerating spent catalysts and/or recovering nickel from spent catalysts and other nickel-containing waste materials since nickel is an expensive metal to be discarded and, moreover, the safe disposal of waste nickel requires consideration of environmental hazards. Several procedures have been described in the prior art for regenerating spent catalysts. U.S. Pat. Nos. 1,306,871; 3,926,842; 4,029,495 and 4,120,698 are examples of such disclosures.
One of the difficulties involved in regenerating spent nickel catalysts results from the presence of reaction contaminants such as the various organic materials being treated by the catalyst systems. One method for removing the organic products which contaminate the spent catalysts is by burning off these organic materials at the same time that any nickel in elemental form is oxidized to form nickel oxide. U.S. Pat. No. 1,306,871 describes such a process for oxidizing spent nickel catalysts to remove organic material and form nickel oxide. The patent also describes the transformation of the nickel oxide to nickel by reduction in a current of hydrogen at a temperature of about 300.degree. C.
The regeneration of a nickel catalyst from spent catalyst is tedious, time consuming, and requires careful attention to the details of the procedure. Therefore, there continues to be a need for methods of recovering nickel from spent catalysts which provide for the inexpensive recovery of the nickel in a usable form.
Nickeliferrous ores, in particular laterite ores containing nickel, have been treated pyrometallurgically to recover ferronickel. One example of a pyrometallurgical process for recovering ferronickel from nickel laterite ores involves operation steps whereby the ore is dried, ground to a powder, calcined, smelted, and finally subjected to reducing conditions to form ferronickel which is separated from the slag.
The amount of ferronickel and the amount of nickel in the ferronickel obtained by such pyrometallurgical processes will depend upon a variety of factors such as the nickel content of the ore, the type and amount of impurities in the ore, and various process parameters, many of which can be varied in accordance with the techniques known to those skilled in the art. It generally is desirable to produce ferronickel having a high concentration of nickel.